#include "texture_loader_pkm.h"
#include "os/file_access.h"
#include <string.h>

struct ETC1Header {
	char tag[6]; // "PKM 10"
	uint16_t format; // Format == number of mips (== zero)
	uint16_t texWidth; // Texture dimensions, multiple of 4 (big-endian)
	uint16_t texHeight;
	uint16_t origWidth; // Original dimensions (big-endian)
	uint16_t origHeight;
};

RES ResourceFormatPKM::load(const String &p_path, const String &p_original_path, Error *r_error) {

	if (r_error)
		*r_error = ERR_CANT_OPEN;

	Error err;
	FileAccess *f = FileAccess::open(p_path, FileAccess::READ, &err);
	if (!f)
		return RES();

	FileAccessRef fref(f);
	if (r_error)
		*r_error = ERR_FILE_CORRUPT;

	ERR_EXPLAIN("Unable to open PKM texture file: " + p_path);
	ERR_FAIL_COND_V(err != OK, RES());

	// big endian
	f->set_endian_swap(true);

	ETC1Header h;
	ERR_EXPLAIN("Invalid or Unsupported PKM texture file: " + p_path);
	f->get_buffer((uint8_t *)&h.tag, sizeof(h.tag));
	if (strncmp(h.tag, "PKM 10", sizeof(h.tag)))
		ERR_FAIL_V(RES());

	h.format = f->get_16();
	h.texWidth = f->get_16();
	h.texHeight = f->get_16();
	h.origWidth = f->get_16();
	h.origHeight = f->get_16();

	DVector<uint8_t> src_data;

	uint32_t size = h.texWidth * h.texHeight / 2;
	src_data.resize(size);
	DVector<uint8_t>::Write wb = src_data.write();
	f->get_buffer(wb.ptr(), size);
	wb = DVector<uint8_t>::Write();

	int mipmaps = h.format;
	int width = h.origWidth;
	int height = h.origHeight;

	Image img(width, height, mipmaps, Image::FORMAT_ETC, src_data);

	Ref<ImageTexture> texture = memnew(ImageTexture);
	texture->create_from_image(img);

	if (r_error)
		*r_error = OK;

	return texture;
}

void ResourceFormatPKM::get_recognized_extensions(List<String> *p_extensions) const {

	p_extensions->push_back("pkm");
}

bool ResourceFormatPKM::handles_type(const String &p_type) const {

	return ObjectTypeDB::is_type(p_type, "Texture");
}

String ResourceFormatPKM::get_resource_type(const String &p_path) const {

	if (p_path.extension().to_lower() == "pkm")
		return "ImageTexture";
	return "";
}